Elasticity is typically added to proper positions, such as legs and a waist, in an absorbent article, for example, a disposable diaper in order to improve a fit to the surface of a body. Conventionally, a technique of securing an elongated resilient and elastic member, such as a rubber thread, that has stretched in a longitudinal direction, has been widely adopted as an exemplary technique of adding elasticity. In a case where elasticity is added with a degree of width, a mode of securing rubber threads arranged with intervals in a width direction, has been adopted.
Meanwhile, a stretchable sheet having a nonwoven fabric/elastomeric film/nonwoven fabric structure, has been proposed in consideration of performing pressing to an elongated face to add elasticity in addition to texture, instead of the plurality of rubber threads arranged in parallel (e.g., Patent Literature 1).
Patent Literature 1 discloses a porous mode in which a hole that penetrates through the entirety of a first outer layer, a second outer layer, and a resilient film (an elastomer), is formed, in addition to a nonporous mode in which no hole is formed through the entirety of the first outer layer, the second outer layer, and the elastic film.
In a case where the stretchable sheet in the nonporous mode is used, for example, as a sheet included in the back surface of a disposable diaper, there is a problem that stuffiness occurs due to no air permeability.
Meanwhile, in the porous mode in Patent Literature 1, the resilient film that is continuous and stretches and contracts in a machine direction (MD) is supplied between the first outer layer and the second outer layer, the elastic film having a melting point higher than those of the outer layers or no melting point, and then the first outer layer and the second outer layer are directly joined together by welding at a predetermined position. After that, tensile force acts in a CD direction to form a through-hole penetrating through the entirety of the first outer layer, the resilient film, and the second outer layer, at a joined site, so that air permeability is secured.
In any case, when the resilient film (the elastomer) stretches in the machine direction, a so-called neck-in phenomenon in which the width of the resilient film shortens, occurs. The resilient film having a width wider than the respective widths of the first outer layer and the second outer layer, is required to be prepared in order to acquire a laminated film having a desired width with the occurrence of the neck-in, resulting in the high cost of materials.
A phenomenon in which there is a difference in stretching and contracting stress between the center in a width direction and both side portions in the width direction, occurs in the CD direction of the sheet to be laminated in practice, together with the neck-in of the resilient film. In a case where the stretchable sheet that has been laminated is applied to a product, for example, a disposable diaper, a problem may occur that uniform stress may not be acquired.